The present invention relates to planetary gear systems used in automatic transmissions.
Japanese Patent Provisional (unexamined) Publication No. 50-64660 discloses one conventional example. The planetary gear system of this conventional example has three single planet type gear sets, as shown in FIG. 47 of the drawings. The gear train shown in FIG. 47 has a first rotary member M1 composed of second and third sun gears, a second rotary member M2 formed by a third carrier, a third rotary member M3 composed of a first ring gear, a second carrier and a third ring gears, a fourth rotary member M4 composed of a second ring gear and a first carrier, and a fifth rotary member M5 formed by a first sun gear. The gear system further includes a connecting means which connects each of input shaft, output shaft, and case (or housing) with one or more of the five rotary members directly or through a selective engaging element such as a clutch or a brake. The input shaft is connected to the fifth, third and first rotary members M5, M3 and M1, respectively, through first, second and third clutches C1, C2 and C3. The fifth, fourth and third rotary members M5, M4 and M3 are connected with the case through first, second and third brakes B1, B2 and B3. The second rotary member M2 is connected directly to the output shaft. This gear system provides six forward speeds including a direct drive speed, and two reverse speeds by engaging two of the selective engaging elements simultaneously, as shown in a diagram of FIG. 48 and a logic table of FIG. 49.
This conventional gear system having three planetary gear sets is disadvantageous in the number of component parts, the manufacturing cost and the axial length of the gear train.